Composite doctoring blade for a heated fuser roll utilized for fixing toner

ABSTRACT

Contact fuser apparatus for fixing toner images to support sheets where the toner images contact a heated fuser roll structure which forms a nip with a resilient backup roll. A sump is provided for applying release material to the heated fuser member by virtue of movement of the fuser member through the release material contained in the sump. A composite doctoring blade structure engaging the fuser member meters the release material to a predetermined thickness and comprises a part of the sump. In order to prevent buckling of the composite structure due to thermal influences, the composite structure is loosely supported so it can expand freely due to such thermal influences.

United States Patent 1 1 Bar-on Oct. 21, 1975 [54] COMPOSITE DOCTORINGBLADE FOR A 3,795,221 3/1974 Michael 118/261 HEATED FUSER ROLL UTILIZEDFOR 3,811,821 5/1974 Ariyama 432/60 FIXING TONER 3,818,861 6/1974 Turner118/261 [75] Inventor: Ari Bar-on, Rochester, NY. Primary ExaminerMervin Stein [73] Assignee: Xerox Corporation, Stamford, AssistantEXaminrDUglaS Sal Conn. v [22] Filed: June 24, 1974 ABSTRACT 2 1 App] 475 Contact fuser apparatus for fixing toner images to support sheetswhere the toner images contact a heated fuser roll structure which formsa nip with a resilient [52] -U.S. C1. 118/60; 118/261; 118/637; backuprolL A Sump is provided for applying release 2 432/60 material to theheated fuser member by virtue of [51] hit. C1. BC 11/04 movement of thefuSer member through the release [58] Field of Search 118/637, 60, 261;material containedv in the sump A Composite doctop 117/17-5; 355/; 432/;101/425 ing blade structure engaging the fuser member meters the releasematerial to a predetermined thickness and [56] References C'tedcomprises a part of the sump. In order to prevent UNITED STATES PATENTSbuckling of the composite structure due to thermal in- 3 552 g5 1/1971Royka at 1 355/15 fluences, the composite structure is loosely supported3,660,863 5/ 1972 Gerbasi 1 355/15 S0 it can expand freely due to suchthermal influences. 3,742,551 7/1973 Oriel 355/15 3,743,407 7/1973 Smith118/637 7 Clams, 10 Drawmg Flgures A we 68 I 7 I36 r 68 US. Patent Oct.21, 1975 Sheetlof6 3,913,521

U.S. Patent Oct. 21, 1975 Sheet2of6 3,913,521

U.S. Patent Oct. 21, 1975 Sheet5of6 3,913,521

U.S. Patent Oct. 21, 1975 Sheet6of6 3,913,521

COMPOSITE DOCTORING BLADE FOR A HEATED FUSER ROLL UTILIZED FOR FIXINGTONER BACKGROUND OF THE INVENTION This invention relates generally toxerographic copying apparatus and, more particularly, to a contactfusing system for fixing electroscopic toner material to a supportmember.

In the process of xerography, a light image of an original to be copiedis typically recorded in the form of a latent electrostatic image upon aphotosensitive member with subsequent rendering of the latent imagevisible by the application of electroscopic marking particles, commonlyreferred to as toner. The visual image can be either fixed directly uponthe photosensitive member or transferred from the member to a sheet ofplain paper with subsequent affixing of the image thereto.

In order to permanently affix or fuse electroscopic toner material ontoa support member by heat, it is necessary to elevate the temperature ofthe toner material to a point at which the constituents of the tonermaterial coalesce and become tacky. This action causes the toner to beabsorbed to some extent into the fibers of the support member which, inmany instances, constitutes plain paper. Thereafter, as the tonermaterial cools, solidification of the toner material occurs causing thetoner material to be firmly bonded to the support member. In both thexerographic as well as the electrographic recording arts, the use ofthermal energy for fixing toner images onto a support member is old andwell known.

One approach to thermal fusing of electroscopic toner images onto asupport has been to pass the support with the toner images thereonbetween a pair of opposed roller members, at least one of which isinternally heated. During operation of a fusing system of this type, thesupport member to which the toner images are electrostatically adheredis moved through the nip formed between the rolls with the toner imagecontacting the fuser roll to thereby effect heating of the toner imageswithin the nip. By controlling the heat transferred to the toner,virtually no offset of the toner particles from the copy sheet to thefuser roll is experienced under normal conditions. This is because theheat applied to the surface of the roller is insufficient to raise thetemperature of the surface of the roller above the hot offsettemperature of the toner whereat the toner particles in the image areasof the toner would liquify and cause a splitting action in the moltentoner to thereby result in hot offset. Splitting occurs when thecohesive forces holding the viscous toner mass together is less than theadhesive forces tending to offset it to a contacting surface such as afuser roll.

Occasionally, however, toner particles will be offset to the fuser rollby an insufficient application of heat to the surface thereof (i.e. coldoffsetting); by imperfections in the properties of the surface of theroll; or by the toner particles insufficiently adhering to the copysheet by the electrostatic forces which normally hold them there. Insuch a case, toner particles may be transferred to the surface of thefuser roll with subsequent transfer to the backup roll during periods oftime when no copy paper is in the nip.

Moreover, toner particles can be picked up by the fuser and/or backuproll during fusing of duplex copies or simply'from the surroundings ofthe reproducing apparatus.

One arrangement for minimizing the foregoing problems, particularly thatwhich is commonly referred to as offsetting has been to provide a fuserroll with an outer surface or covering of polytetrafluoroethylene,commonly known as Teflon, to which a release agent such as silicone oilis applied, the thickness of the Teflon being on the order of severalmils and the thickness of the oil being less than 1 micron. Siliconebased oils, which possess a relatively low surface energy, have beenfound to be materials that are suitable for use in the heated fuser rollenvironment where Teflon constitutes the outer surface of the fuserroll. In practice, a thin layer of silicone oil is applied to thesurface of the heated roll to thereby form an interface between the rollsurface and the toner images carried on the support material. Thus a lowsurface energy layer is presented to the toner as it passes through thefuser nip and thereby prevents toner from offsetting to the fuser rollsurface.

A fuser roll construction of the type described above is fabricated byapplying in any suitable manner a solid layer of abhesive material to arigid core or substrate, such as the solid Teflon outer surface orcovering of the aforementioned arrangement. The resulting roll structureis subject to degradation due to continued operation at elevatedtemperatures and also to damage from accidental gouging by stripperfingers conventionally employed in such systems. The foregoing in manyinstances necessitates replacement of the fuser roll which is quitecostly when a large number of machines are involved. I

Moreover, since a several mil thickness of polytetrafluoroethylene alongwith the coating of silicone oil constitutes a poor thermal conductor,longer nip dwell and higher fuser roll temperatures are required todeliver the fusing energy required. Also, control of the surfacetemperature of the roll presents a problem due to large temperaturevariations occurring before and after contacting of the substratecarrying the images.

In view of the foregoing, it would appear that the high thermalconductivity and wear resistance of bare metals or similar materialswould be desirable for utilization in fuser roll structures, however,such materials have, heretofore, not been found satisfactory for suchapplication. The latter is attributable to-the very high surface energyof metals and similar materials which renders them readily wettable byhot toner materials. Once wetted by hot toner, it has been verydifficult if not impossible to remove the toner from such materialswhile they remain hot. Commonly used release agents such as puresilicone oils have been tried in combination with various metals andother high surface energy materials but with relatively little or nosuccess. One release agent or material suitable for use with bare metalrolls is a low molecular weight polyethylene commercially available fromthe Allied Chemical Company under the designation AC-8 homopolymer. Thisparticular release material is solid at room temperature. Conventionalrelease material applicators have not been found suitable for applyingrelease materials which are solid at room temperature.

Accordingly, the principal object of this invention is to provide a newand improved heat and pressure fuser for fixing toner images to supportsheets.

It is a more particular object of this invention to provide a new andimproved structure for applying release material to a heated fusermember utilized for fixing toner images to support sheets.

Anotherobject of this invention is to provide a new and improvedstructure for metering release material applied to a heated fuser memberto a desired thickness.

Still another object of this invention is to provide a structure formetering release material to a heated fuser member the metering of whichis not adversely effected from the thermal energy of the heated fuser.

BRIEF SUMMARY OF THE INVENTION Briefly, the above-cited objects areaccomplished by y the provision of'a heat and pressure fuser structurefor fixing toner images to support sheets. The fuser structure ischaracterized by the provision of a sump containing release material tobe applied to a heated member of the fuser. The heated fuser member issupported relative to the sumps such that a portion thereof contacts therelease material which during operation is liquid and at roomtemperature is a solid. While the detailed description of the preferredembodiment discloses a release material that is a solid at roomtemperature, it will be appreciatd that other release materials can beapplied and metered to the fuser member by the specific means disclosedfor such purposes. For exam- 1 member. The blade structure comprises arectangularshaped base member which is preferably fabricated ofstainless steel and is approximately 0.007 inch thick. A strip ofelastomeric material, for example, temperature resistant silicone rubberor Viton the latter being a trademark of Dupont is affixed adjacent oneedge of the base while the other end of the base is attached to the sumpand forms the front wall thereof. The means for attaching the basemember allows for expansion thereof due to thermal influences from theheated member. A seal member fabricated from a closed cell siliconesponge rubber material is affixed tothe sump and engages the edge of thebase member opposite the rubber strip to prevent the release materialfrom leaking out of the sump without impeding the thermal expansion ofthe base.

Other objects and advantages of the present inven-- tion will becomeapparent when read in conjunction with the accompanying drawingswherein:

FIG. 1 is a schematic representation of a xerographic reproducingapparatus incorporating the novel image fuser of the present invention;

FIG. 2 is a top plan view of a fuser assembly incorporated in FIG. 1;

FIG. 3 is a right side elevational view of the fuser assembly of FIG. 2;

FIG.'4 is a cross-sectional view taken on the line IV-IV of FIG. 3;

FIG. 5 is an enlarged fragmentary view in section of a release agentdoctoring structure forming a part of the fuser assembly of FIGS. 2 thru4;

FIG. 6 is a perspective view of the composite doctoring structure ofFIG. 5;

FIG. 7 is an elevational view of the fuser assembly as viewed from theleft in FIG. 3;

FIG. 8 is a perspective view of a copy sheet stripper finger;

FIG. 9 is a cross-sectional view of a fuser roll system showing amodified stripper finger arrangement and a backup roll cleaningstructure; 7

FIG. 10 is a cross-sectional view of a sprocket drive and one-way clutcharrangement incorporated in the fuser assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The reproducing machineillustrated in FIG. 1 employs an image recording drum-like member 10 theouter periphery of which is coated with a suitable photoconductivematerial 11. One type of photoconductive material is disclosed in U.S.Pat. No. 2,970,906 issued to Bixby in 1961. The drum 10 is suitablyjournaled for rotation within a machine frame (not shown) by means of ashaft 12 and rotates in the direction indi cated by arrow 13, to bringthe image retaining surface thereon past a plurality of xerographicprocessing stations. Suitable drive means (not shown) are provided topower and coordinate the motion of the various cooperating machinecomponents whereby a faithful reproduction of the original input sceneinformation is recorded upon a sheet of final support material such aspaper or the like.

Since the practice of xerography is well known in the art, the variousprocessing stations for producing a copy of an original are hereinrepresented in FIG. 1 as blocks A to E. Initially, the drum movesphotoconductive surface 11 through a charging station A. At chargingstation A an electrostatic charge is placed uniformly over thephotoconductive surface 11 of the drum l0 preparatory to imaging. Thecharging may be provided by a corona generating device of a type de- No.2,836,725 issued to Vyverberg A suitable exposure system may be of thetype de-' scribed in U.S. Pat. Application, Ser. No. 259,181 filed June2, 1972. j A

After exposure, drum 10 rotates the electrostatic latent image recordedon the photoconductive surface 1 l to development station C, wherein aconventional developer mix is applied to the photoconductive surface 11of the drum l0 rendering the latent image, visible. A suitabledevelopment station is disclosed in U.S. Pat. Application, Ser. No.199,481 filed Nov. 17, 1971. This application describes a magnetic brushdevelopment system utilizing a magn'etiz'able developer mix havingcarrier granules and'tonr comprising electrophotographic resin pluscolorant from dyes or pigments. A developer mix is continually broughtthrough a directional flux field to form a brush thereof. Theelectrostatic latent image recorded on photoconductive surface 11 isdeveloped by bringing the brush of developer mix into contact therewith.The developed image on the photoconductive surface 11 is then broughtinto contact with a sheet of final support material 14 within a transferstation D and the toner image is transferred from the photoconductivesurface 11 to the contacting side of the final support sheet 14. Thefinal support material may be plain paper, gummed labels, transparenciessuch as Polycarbonate, Polysulfane and Mylar, etc., as desired.

After the toner image has been transferred to the sheet of final supportmaterial 14, the sheet with the image thereon is advanced to a suitablefuser assembly 15 which fuses the transfer powder image thereto. Afterthe fusing process, the final support material 14 is advanced by aseries of rolls 16 to a copy paper tray 17 for subsequent removaltherefrom by a machine operator.

Although a preponderence of the toner powder is transferred to the finalsupport material 14, invariably some residual toner remains on thephotoconductive surface 11 after the transfer of the toner powder imageto the final support material 14. The residual toner particles remainingon the photoconductive surface 11 after the transfer operation areremoved from the drum 10 as it moves through cleaning station E. Herethe residual toner particles are first brought under the influence of acleaning corona generating device (not shown) adapted to neutralize theelectrostatic charge remaining on the toner particles. The neutralizedtoner particles are. then mechanically cleaned from the photoconductivesurface 11 by conventional means as for example, the use of aresiliently biased knife blade as set forth in US. Pat. No. 3,660,863issued to Gerbasi in 1972.

The sheets of final support material 14 processed in the automaticxerographic reproducing device may be stored in the machine within aremovable paper cassette 18. A suitable paper cassette is set forth inU.S. Pat. Application, Ser. No. 208,138 filed Dec. 15, l97l.

The copier can also have the capability of accepting and processingcopying sheets of varying lengths. The length of the copy sheet, ofcourse, being dictated by the size of the original input sceneinformation recorded on the photoconductive surface 11. To this end, thepaper cassette 18 is preferably provided with an adjustable featurewhereby sheets of varying length and width can be convenientlyaccommodated therein.

In operation, the cassette 18 is filled with the stack of final supportmaterial 19 of pre-selected size and the cassette 18 is inserted intothe machine by sliding along a baseplate (not shown) which guides thecassette 18 into operable relationship with a pair of feed rollers 20.When properly positioned in communication with the feed rollers 20 thetop sheet of the stack 19 is separated and fowarded from the stack 19into the transfer station D by means of registration rollers 21.

It is believed that the foregoing description is sufficient for purposesof present application to illustrate the general operation of anautomatic xerographic copier which can embody the teachings of thepresent invention.

The fuser assembly 15 as best illustrated in FIGS. 2 through 4 comprisesa heated fuser roll structure 30 and a backup roll 32 which cooperate toform a nip 33 therebetween through which copy paper having toner imagesthereon passes with the toner images contacting the fuser roll structure30.

A channel shaped support base 34 (FIG. 3) is provided for supporting thefuser assembly 15 in the copier apparatus. The backup roll 30 issupported by a pair of support brackets 36 which are secured to thesupport base 34 by means of right angle brackets 38, the bases of whichare spot welded or otherwise suitably affixed to the support base 34. Apair of ball bearings 40 are supported by the brackets 36 and arecaptivated in the brackets by means of retaining rings 42. The backuproll structure may comprise any suitable construction, for example, asteel cylinder, but preferably comprises a rigid steel core or shaft 46having a Viton elastomer surface or layer 48 disposed thereover andaffixed thereto. A pair of shaft ends 49 of the core or shaft 46 arereceived in the bearings 40 for supporting the backup roll 30. Asuitable backup roll has an overall dimension of approximately 1.55inches including a 0.1 inch cover or layer of Viton elastomer or othersuitable high temperature elastomeric material, for example,fluorosilicone or silicone rubber. The specific dimensions of the backuproll will be dictated by the requirements of the particular copyingapparatus wherein the fuser assembly 15 is employed, the dimensionsbeing greater or less depending upon the process speed of the machine.In this embodiment the length of the roll is approximately 15 inches toaccomodate various paper sizes.

A pair of support brackets 50 (FIG. 2) having a generally E-shapedconfiguration similar to the support brackets 36 are provided formounting the fuser roll structure in the fuser assembly 15. To this end,a pair of ball bearings 52 one in each of the support brackets 50 areprovided, the bearings being retained in the brackets by means ofretaining rings 54. A pair of end caps 55 are secured to a hollowcylinder or core 56 (FIGS. 3 and 4) forming a part of the fuser rollstructure 30 and reduced portions 57 thereof are received in thebearings 52 for supporting the fuser roll structure. A heating element58 is supported internally of the core 56 for providing thermal energyto elevate the temperature of the core to operating limits. The heatingelement may comprise any suitable type heater for elevating the surfacetemperature of the cylinder to operational temperatures, therefore285290F. For example, it may be a quartz envelope having a tungstenresistance heating element disposed therein. The cylinder or core 56 isfabricated from any suitable material capable of efficiently conductingthe heat to the external surface of the core. Typical materials areanodized aluminum and alloys thereof, steel, stainless steel, nickel andalloys thereof, nickel plated copper, chrome plated copper, copperandalloys thereof. The resulting structure has an outside diameter onthe order of 1.5 inches and has a length equal to that of the backuproll. The power requirements for the foregoing are 420 watts peak powerwith an average power of 320 watts and 100 watts for standby.

The heater element 58 is supported internally of the core 56 by a pairof spring supports 60 which are mounted by insulator blocks 62 to thesupport brackets 50. The free ends of the springs supporting the heaterelement are each provided with a locating ball 64 while the opposite endof the spring is disposed in contact with an electrical terminal 66 towhich electrical wires (not shown) may be attached for supplyingelectrical energy to the heater element. The terminal blocks can besecured to the support brackets in any suitable manner, for example, byscrews. The springs supports and terminals are preferably rivoted to theterminal block.

The aforementioned materials from which the core 56 of the fuser rollstructure may be fabricated are relatively high surface energymaterials, consequently, hot toner material contacting such surfaceswould readily wet the surface of the fuser roll and it would bedifficult to remove the toner therefrom. Accordingly, there is provideda sump 68 (FIGS. 2 and 4) for containing a material 69 capable ofinteracting with the core in a manner described in U.S. Pat.Application, Ser. No. 383,231 filed July 27, 1973 in the name of Moser,et al and assigned to the same assignee as the instant application. Thematerial is preferably a low molecular weight substance homopolymer issolid at room temperature and which has a relatively low viscosity atthe operating temperatures of the fuser roll structure. An example ofsuch a material is polyethylene homoploymer manufactured by AlliedChemical Co. and having the designation AC-8 hopolymer.

The sump 68 comprises a rear wall 70 having a generally sloping portionconnected to a generally vertical portion. The rear wall is providedwith a pair of apertured flanges 72 for receiving supports 74 formounting the sump 68 to the flanges 51 secured to the brackets 50 in amanner to allow pivotal movement thereof. The sump also comprises afront wall (FIG. which comprises a composite doctoring blade 78including a base member 80 with an elongated strip 82 secured to thebase member. The strip 82 is fabricated from a high temperatureelastomeric material which is compatible with the particular material69, for example, silicone rubber or Viton. By compatible with the stripit is meant that the dimensions of the strip are not altered by contactwith the material.

The base member 80 and therefore the blade 78 is supported by the rearwall 70 by means of a rubber seal attached to a lip 84 forming a part ofthe rear wall and a retainer 86 which is suitably secured by, forexample, screws 87, to the rear wall 70. The base member 80 is providedwith a plurality of slots 88 in which the screws 87 ride to allowmounting of the base member intermediate the retainer 86 and the rearwall 70. The base member is also provided with a plurality of apertures90 disposed on the sides of the slots 88. The apertures receive dimples92 forming a part of the retainer 86. The slots and the apertures areoversized with respect to the dimples and screws so that the base membercan move due to thermal expansion without buckling thereof. It will beappreciated that in addition to serving as a metering blade thecomposite structure 78 serves to clean toner from the fuser rollstructure 30 and also act as a seal to prevent the liquid or lowviscosity polyethylene from leaking out of the sump 68. A pair ofarcuate recesses 94 provided in the rear wall 70 have disposed thereinend seals 96 which contact the fuser roll structure and therebycooperate with the strip 82 to prevent leakage of polyethylene from thesump.

A pair of links 100 attached to extensions 101 of the rear wall byretaining pins 102 have their ends threaded for receiving nuts 104. Atie bar 106 attached to the support brackets 50 support L-shap'edbrackets 108 having slots 110 therein. The links 100 are received in theslots 110 to thereby provide means for adjusting the pivotal orientationof the sump 68 to thereby increase or decrease the pressure of thecomposite doctoring structure 78 on the fuser roll structure to therebycontrol in accordance with a predetermined amount, for

example, a layer less than 1 micron thick, the application ofpolyethylene to the fuser roll structure. This is accomplished bytightening or loosening of the nuts As mentioned hereinbefore, thepolyethylene is solid at room temperature and is liquid at operationaltemperatures. The polyethylene in solid form is placed in the sump andis heated by the thermal energy of the fusing roll structure and therebyliquified- When the polyethylene resolidifies after the machine has beeninoperative for a period of time the polyethylene tends to move awayfrom the fuser roll structure consequently when the machine is restartedthe polyethylene may not be applied to the fuser roll structureimmediately. This means that the fuser roll structure may not beproperly protected against toner offsetting to the bare metal. In orderto safeguard against the foregoing, the surface of therear wallcontacting the polyethylene is coated with a material that has a lowaffinity for the polyethylene, for example, silicone rubber. In order toinsure that the polyethylene is in contact with the fuser roll structureat the time of restarting the machine, a collecting bar 1 11 is providedin the sump and attached thereto such that it is positioned adjacent thefuser roll structure. Accordingly, when the polyethylene resolidifies itwill pull away from the rear wall and it will solidify on the collectingbar such that it is still in contact with the fuser roll structure. Thisarrangement will insure proper operation of the fuser assembly until thebulk of the polyethylene is melted in the sump.

The axis of the backup roll which should be apparent from aconsideration of its mounting as discussed above is fixed relative tothe support base 34. However, the fuser roll structure is mounted suchthat its pressure engagement with the backup roll can be adjusted tothereby enable variation of the length of the nip 33 formed between thetwo roll structures. To thie end, the fuser roll support brackets 50 aremounted to the backup roll support brackets 36 by a pair of flexures 112which are secured to the support brackets 36 and 50 by means ofretaining plates 114, dowl pins 116 and caps screws 118. The flexures112 are preferably fabricated from spring steel having a relativelysmall thickness but sufficiently sturdy to hingedly mount the fuser rollsupport brackets to the backup roll support brackets. A force at the nipon the order of 150 pounds is provided by means of socket head screws120 and commercial compression springs 122 which are supported by theupper flanges 51 secured to the fuser roll support brackets 50. Thescrews 120 are received in threaded lower flanges 126 which are fixedlymounted to the backup roll support brackets 36. It will be appreciatedthat by adjusting the socket head screws 120 against the force exertedby the springs 122, the nip pressure can be varied to produce thedesired nip pressure.

The copy paper 14 carrying the fused images comprising toner 124 ismoved through a lower guide plate 128 (FIG. 4) which is supported bymounting brackets 129 attached to the backup roll supporting brackets 36and an upper guide plate 130 attached to the tie bar .106. The upperguide plate is mounted to the tie bar by means of a generally U-shapedflange 132 having an open area which is integral with the plate 130 anddisposed at an acute angle relative thereto. To insure that the copypaper follows along a predetermined path including the space between thelower and upper guide plates a plurality of generally L-shaped stripperfingers 134 (FIGS. 4 and 8), preferably two in number, are provided. Theleading edges of the stripper fingers are biased into engagement withthe fuser roll structure by means of a pair of combination mountingbrackets and bias member 136 in the form of leaf springs. The leafsprings are mounted to the tie bar 106 such that a cantilevered portion137 thereof engages a cam surface 138 of the stripper finger 134.Portions of the mounting bracket 136 are rolled as indicated at 140 toprovide a bearing surface for shafts 141 carried by the stripper fingers134.

An alternate form of stripper finger may be employed which comprisesstripper fingers 142 (FIG. 9) supported on a shaft 143 which issupported indirectly by the support brackets 50 of the fuser rollstructure 30. A counterweight 144 is provided for each of the stripperfingers 142 and is secured thereto by means of a cap screw 145 which isthreaded into the stripper finger. The position of thecounterweight canbe varied relative to the stripper finger to increase or decrease theamount of pressure which is applied by the stripper finger to the fuserroll structure. The position of the stripper fingers 142 are maintainedon the shaft in a position relative to the longitudinal axis of thefuser roll structure 30 by grip rings 146. The grip rings whilemaintaining the position of the stripper fingers fixed relative thefusing roll structure 30 allow movement relative to the aforementionedaxis of the stripper fingers with respect to the fuser roll structure sothat the fuser stripper fingers can be repositioned in the event of wearof the fuser roll structure.

The surface temperature of the fuser roll structure 30 is controlled bycontacting the surface thereof with a thermistor probe 148 of the typedescribed in U.S. Pat. No. 3,327,096, issued in 1967 to Bernous andincorporated herein by reference.

During operation of the fuser assembly 15, particularly during duplexcopying, toner accumulates on the backup roll structure 32. Accordingly,a -backup roll cleaning structure or assembly 150 is provided whichcomprises a triangular shaped support member 152 having a wiper member153 carried thereby. The cleaning assembly is supported for movement inthe direction of the backup roll structure by a plurality of rollersupports 154 and a spring member 156 supported by a member 158 urges thewiper surface into wiping contact with the backup roll. As can be seenfrom the drawings, the cleaning assembly is disposed adjacent thesupport base 34 so that toner removed from the backup roll will bedeposited onto the support base. In operation it has been found that thetoner accumulates on the exit side of the nip formed between the backuproll and the wiper member. The wiper member is preferably a hightemperature material with a high degree of resiliency and low affinityfor toner particles and preferably comprises tetrafluoroethylene,commonly referred to as TFE. I

In order to accomplish rotational movement of the fuser and backuprolls, the main machine drive is coupled to the fuser roll structure viaa drive sprocket 160, which is coupled to a driven sprocket 161 by meansof a one-way clutch 162, a bushing 164, and stub shaft 166. The drivensprocket 161 is coupled to a sprocket carried by the shaft of the fuserroll structure 30 via a chain 172. The clutch 162 serves as a couplingbetween the input from the main machine drive and the fuser rollstructure, which allows the fuser roll structure and backup roll to berotated independently of the sprocketsprovided for power driving thefuser roll structure. In the event that a machine jam occurs, a sheet ofcopy paper which has started through the nip of the fuser assembly 15can be manually moved out of the fuser assembly while simultaneouslyfusing the toner images to the copy paper. Accordingly, unlike prior artfuser structures utilized in the xerographic process, a copy which hasstarted through the fuser but has not been completely fused can be savedbecause it can be fused notwithstanding a paper jam.

A cover structure 174 protects the fuser assembly from contaminates. Asviewed in FIG. 7, the cover structure has a bifurcated flange portion176 which receives a pin member 178 carried by the bracket 50. There aretwo such flanges and pin members, one on each side of the fuserassembly. A sidewardly projecting flange 180 has an aperture throughwhich a screw 181 is inserted and received in a threaded aperture in aflange 182 forming a part of the sump 68. The combination bifurcatedflanges and pin members together with the screw 181 secures the cover inplace. As viewed in FIG. 3, the cover has an inclined top surface 184and an opening 186 at the extreme right end thereof for directing vaporsout of the fuser assembly. A pair of depending flanges 190 cooperatewith pins 192 carried by the tie bar 106 to assist in maintaining thecover in place.

While the invention has been described with respect to a preferredembodiment, it will be apparent that certain modifications and changescan be made without departing from the spirit and scope of theinvention, for example, the images to be fused can be formed by otherthan the xerographic process disclosed and it is therefore intended thatthe foregoing disclosure be limited only by the claims appended hereto.I

What is claimed is:

1. Contact fuser apparatus for fixing toner images to support sheets,said apparatus comprising:

a heated fuser member;

a resilient backup member supported for cooperation with said heatedmember to pass support sheets therebetween with said toner imagescontacting said heated fuser member;

means for applying release material to the surface of said heated fusermember;

means for doctoring said release material applied to said heated fusermember to a predetermined thickness, said doctoring means comprising acomposite structure including a flexible base member and a resilientstrip, said resilient strip engaging said fuser member; and

means engaging said base member for supporting said composite structurein cantilever fashion, said resilient strip being attached to said basemember adjacent the free end thereof.

2. Apparatus according to claim 1, wherein said means supporting saidcomposite structure permits movement of said base member and said stripdue to thermal expansion to thereby prevent buckling thereof.

3. Apparatus according to claim 2, wherein said release materialapplying means comprises a sump for holding said release material andsaid composite structure comprises one wall thereof.

4. Apparatus according to claim 1, wherein said means for supportingsaid composite structure comprises cooperating means having said basemember sandwiched therebetween in a manner to permit movement relativethereto in response to thermal expansion of said base member to therebyprevent buckling of said composite structure.

5. Apparatus according to claim 4, wherein said release materialapplying means comprises a sump and said composite structure forms onewall thereof.

6. Apparatus according to claim 5, wherein said cooperating meanscomprises a retainer member and another wall of said sump, said retainerbeing fastened to tening said retainer to said another wall.

1. Contact fuser apparatus for fixing toner images to support sheets, said apparatus comprising: a heated fuser member; a resilient backup member supported for cooperation with said heated member to pass support sheets therebetween with said toner images contacting said heated fuser member; means for applying release material to the surface of said heated fuser member; means for doctoring said release material applied to said heated fuser member to a predetermined thickness, said doctoring means comprising a composite structure including a flexible base member and a resilient strip, said resilient strip engaging said fuser member; and means engaging said base member for supporting said composite structure in cantilever fashion, said resilient strip being attached to said base member adjacent the free end thereof.
 2. Apparatus according to claim 1, wherein said means supporting said composite structure permits movement of said base member and said strip due to thermal expansion to thereby prevent buckling thereof.
 3. Apparatus according to claim 2, wherein said release material applying means comprises a sump for holding said release material and said composite structure comprises one wall thereof.
 4. Apparatus according to claim 1, wherein said means for supporting said composite structure comprises cooperating means having said base member sandwiched therebetween in a manner to permit movement relative thereto in response to thermal expansion of said base member to thereby prevent buckling of said composite structure.
 5. Apparatus according to claim 4, wherein said release material applying means comprises a sump and said composite structure forms one wall thereof.
 6. Apparatus according to claim 5, wherein said cooperating means comprises a retainer member and another wall of said sump, said retainer being fastened to said another wall.
 7. Apparatus according to claim 6, wherein said retainer means has at least one pair of dimple members engaging said another of said walls and acting as standoffs providing suitable spacing between said cooperating means to permit free movement of said base member, said base member being provided with openings receiving said dimples and the means for fastening said retainer to said another wall, said openings being slightly larger than said dimples and said means for fastening said retainer to said another wall. 